STT: add ninja "explain" to see the reason of build triggers

verbose.log.gz includes the logs for the ninja explain.
The logs will be automatically cached to verbose.log.gz,
verbose.log.2.gz, and verbose.log.4.gz.

Bug: 284915566
Test: combined_build_test.sh -t cf_x86_64_phone -v userdebug \
                   -d out/dist -a cf_x86_64_foldable -o -c -r droid
Change-Id: Ib722a7c331cfe6b034ab4812b85504d2f5161881
1 file changed